Bagasse Cellulose Composite Superabsorbent Material with Double-Crosslinking Network Using Chemical Modified Nano-CaCO3 Reinforcing Strategy

Design and preparation of reticular superabsorbent hydrogel material with nutrient slow-release and high shear strength for ecological remediation of abandoned mines with steep slopes

In order to solve ecological remediation issues for abandoned mines with steep slopes, a kind of hydrogels with high cohesion and water-retaining were designed by inorganic mineral skeleton combining with polymeric organic network cavities. This eco-friendly hydrogel (MFA/HA-g-p(AA-co-AM)) was prepared with acrylic acid (AA)-acrylamide (AM) as network, which was grafted with humic acids (HA) as network binding point reinforcement skeleton and polar functional group donors, KOH-modified fly ash (MFA) as internal supporter. The maximum water absorption capacities were 1960 g/g for distilled water, which followed the pseudo-second-order model. This super water absorption was attributed to the first stage of 62 % fast absorption due to the high specific surface area, pore volume and low osmotic pressure, moreover, the multiple hydrophilic functional groups and network structure swell contributed to 36 % of the second stage slow adsorption. In addition, the pore filling of water in mesoporous channels contributed the additional 2 % water retention on the third stage. The high saline-alkali resistance correlated with the electrostatic attraction with MFA and multiple interactions with oxygen-containing functional groups in organic components. MFA and HA also enhanced the shear strength and fertility retention properties. After 5 cycles of natural dehydration and reabsorption process, these excellent characteristics of reusability and water absorption capacity kept above 97 %. The application of 0.6 wt% MFA/HA-g-p(AA-co-AM) at 15° slope could improve the growth of ryegrass by approximately 45 %. This study provides an efficient and economic superabsorbent material for ecological restoration of abandoned mines with steep slopes.

Enhanced Water Absorbency and Water Retention Rate for Superabsorbent Polymer via Porous Calcium Carbonate Crosslinking

To improve the water absorbency and water-retention rate of superabsorbent materials, a porous calcium carbonate composite superabsorbent polymer (PCC/PAA) was prepared by copolymerization of acrylic acid and porous calcium carbonate prepared from ground calcium carbonate. The results showed that the binding energies of C-O and C=O in the O 1s profile of PCC/PAA had 0.2 eV and 0.1-0.7 eV redshifts, respectively, and the bonding of -COO- groups on the surface of the porous calcium carbonate led to an increase in the binding energy of O 1s. Furthermore, the porous calcium carbonate chelates with the -COO- group in acrylic acid through the surface Ca2+ site to form multidirectional crosslinking points, which would increase the flexibility of the crosslinking network and promote the formation of pores inside the PCC/PAA to improve the water storage space. The water absorbency of PCC/PAA with 2 wt% porous calcium carbonate in deionized water and 0.9 wt% NaCl water solution increased from 540 g/g and 60 g/g to 935 g/g and 80 g/g, respectively. In addition, since the chemical crosslinker N,N'-methylene bisacrylamide is used in the polymerization process of PCC/PAA, N,N'-methylene bisacrylamide and porous calcium carbonate enhance the stability of the PCC/PAA crosslinking network by double-crosslinking with a polyacrylic acid chain, resulting in the crosslinking network of PCC/PAA not being destroyed after water absorption saturation. Therefore, PCC/PAA with 2 wt% porous calcium carbonate improved the water-retention rate by 244% after 5 h at 60 °C, and the compressive strength was approximately five-times that of the superabsorbent without porous calcium carbonate.

Nanostructure Design of Catalysts: Latest Advances and Prospects

The recent development of nanotechnology has laid the foundation for the design and preparation of various nanostructured materials [...].

Study on the resourceful reuse in SBS-modified asphalt of waste bagasse fibers based on green modification with tannic acid and FeOOH

Hydrophobic modification of bagasse fibers (BFs) through a green approach can promote its reuse in asphalt and enhance the utilization value of agricultural and forestry waste in road engineering. In contrast to traditional chemical modification, this study reports a new method for the hydrophobic modification of BFs using tannic acid (TA) and the in situ growth of FeOOH nanoparticles (NPs), resulting in FeOOH-TA-BF, which is used to prepare styrene-butadiene styrene (SBS)-modified asphalt. The experimental results show that the surface roughness, specific surface area, thermal stability, and hydrophobicity of the modified BF are improved, which is beneficial for enhancing the interface compatibility with asphalt. Specifically, compared with BF/SBS-modified asphalt, FeOOH-TA-BF/SBS-modified asphalt exhibits 39.21% and 23.26% increase in the elastic modulus G' and viscous modulus G″, respectively, at the optimal dosage of 2.5%, corresponding to 6.15-fold and 7.13-fold increase in the fatigue life at 2.5% and 5.0% strain respectively, and 22.0% improvement in shear resistance performance. In the meantime, 2.5-fold enhancement of the storage stability. Therefore, this study provides a simple, environmentally friendly, and efficient hydrophobic modification method that is of great significance for promoting the resource utilization of solid waste BF.